Hot top casing for casting molds



Fig. 3

P. DAVIDSON HOT TOP CASING FOR CASTING MOLDS Filed Dec. 21, 1959 Jan.15, 1963 superior qualities. hot top includes a firm and relatively thincasing consist- United-States Patent Or This invention relates generallyto casting molds used in the casting of steel and other metals and moreparticularly to a hot top casing structure adapted for use with ingotcasting molds.

For a long time there has been a need in the casting hot top art for amold casing material which meets the requirements of good heatinsulation, good form resistance and low manufacturing cost. Whilevarious types :of hot top casings have been provided in the past, thesehave been specifically designed to provide roughened sinkhead surfaceson the cast ingot so that the ingot may be suitably gripped by the tongsof lifting cranes.

An object of the present invention is to provide a cast- .ing mold hot'produces an ingot the sinkhead of which has smooth surfaces so that-thesinkhead part of the ingot may be used during subsequent ingot treatmentrather than being wasted as inthe past.

top casing of simple construction which Another object of the inventionis to provide a hot top which results in orientation of the arisingpipes and liquations extending upwardly in the ingot so that the portionof the ingot being returned as scrap during subsequent ingot treatmentis minimized.

According to the present invention it is possible to manufacture, at lowcost, casting mold hot tops having In accordance with the invention theing of an organic fibrous material, a fireproof material, and a binder,which casing is characterized in that it consists by weight of not lessthan 2% and not more than 20% (preferably not more than 15%) organicfibrous material, 4l0% binder, and the remainder fireproof ma j terial.For the organic fibrous material it has been proven advantageous to usepaper pulp, waste paper or the like-'e.g., mechanical pulp or a pulp ofwaste paper or the like possibly with an addition of chemical pulp. Asfireproof material may be used quartz, sand or another silicate; in somecases basic materials as burned dolomite, cinders, or the like may beused. In the fireproof material may also be included upto by weight of afireproof fibrous vmaterial such as asbestos. The binding medium maybeorganic or inorganic. Of the first type there may be .mentioned glue,such as synthetic glue (e.g. syntheticresins or silicone resin), gluemanufactured from animalor vegetable raw materials (cellulose glue). Ofthe latter type may be mentioned fireproof cement or silicate ofpotassium (water glass). The casing may be completely or partlysurrounded by an insulated volume of air or by a heat insulatingmaterial such as sand, bricks or the like.

It has been shown that hot top casings in accordance with the inventionare relatively inexpensive to manufacture, have good storing and formresistance properties, good insulation qualities, and achieve smoothsurfaces of the cast metal. For example, during the manufacture of asteel ingot with the use of hot top casings in accordance with theinvention the sinkhead obtains a smooth surface as the pipes orliquations are concentrated in its uppermost part. This is of greateconomical importance, since only a very small part of the steel in asinkhead has to be returned as scrap.

Other objects and advantages of my invention will ice become apparentfrom a study of the following specification when considered inconjunction with the accompanying drawings in which:

FIG. 1 is a vertical section of the hot top casing taken along line 11of FIG. 2;

FIG. 2 is a plan view of the hot top casing;

FIG. 3 is a sectional view taken through the mold and hot top;

FIG. 4 is a detailed sectional view of another embodiment of theinvention; and

FIGS. 5-7 are detailed sectional views of other hot top constructions.

As shown in FIGS. 3-5, the hot top casing 13 tapers upwardly andinwardly and is supported at its lower edge on the shoulder portions 16of the wall of the ingot mold 12. It is also possible, however, to placethe hot top casing upon the upper circumferential surface of the ingotmold opening. As mentioned above the casing consists by weight of 220%(preferably 2-15%) organic fibrous material, 4-l0% binder, and theremainder fireproof material. As especially preferred limits there maybe mentioned 25-13% by weight organic fibrous material and 4.5-9%binder. Possibly also smaller quantities of other materials may beincluded. As examples of organic fibrous materials of suitableconsistency may be mentioned paper pulp, waste paper or the like (e.g.mechanical pulp or pulp manufactured from waste paper, possibly havingan addition of chemical pulp). The suitability of the mentioned fiberpulp for thispurpose is that the bin-ding of the usually granular and/or powder-formed fireproof material (e.g. quartz) is facilitated, andalso the casing is given a porosity which substantially increases itsinsulation qualities. It has also been shown that injurious gasformation is avoided by the use of the casing when theabove mentionedcontents of the fibrous material are included.

As fireproof material, quartz or quartzite may be suitably used. Alsoother fireproof materials such as sand, certain other silicates, basicmaterials as burned dolomite and cinders and the like may be used. Ifdesired one may use up to about 10% (preferably 04%) by weight fireprooffiber material (as for example asbestos) mixed in the usually granularand/or powder-formed fireproof material. The medium grain size for thefireproof material is to be below 1 mm., preferably below 0.3 mm. andoften below 0.2 mm. Suitable limits for the medium grain size may be0.6-0.05 mm. The grain size may be stated as being below mesh,preferably below 45 mesh.

The binder in the casing may be glue, such as synthetic glue, e.g.synthetic resin or silicone resin, or glue manufactured of animal orvegetable raw materials such as cellulose glue. Usually a sufficientquantity of binder is added to achieve satisfactory strength. In certaincases instead of the above mentioned binder an inorganic binder such asfireproof cement or water-glass may be used.

As examples of suitable material compositions for the casing inaccordance with the invention may be mentioned the following:

(1) Mass or pulp composed by waste paper and/or other mechanical pulp,possibly mixed with some smaller quantities of chemical pulp, total 242%by weight, synthetic resin, glue or the like, 58% by weight, and theremainder fireproof material, preferably quartzite powder and/ or thelike.

(2) Paper pulp and/or waste paper, 2-8% by weight, glue 5'8% and therest consisting of fireproof material.

(3) Paper pulp -3-12% by weight (preferably about 3%), asbestos 0.4%(preferably above 0%), glue 5-8% and the rest fireproof material.

As shown in FIGS. 1-2, the hot top casing 13 is formed angle of 2-15,.preferably 2-10.

of course. be supportedby an outer casing and its lower edge may duringrolling; the ingot is materially. reduced.

12 (FIG. 3

The shoulder surface 16 is inclined to the vertical at an For smalldiameter variationsbetween the ingot molds of the same type and size thecasing will be applied in such a way upon the ingot mold that the totalvolume included in the casing and ingot mold (and thus the .ingotweight) will be substantially constant.

In the embodiment of FIG. 3, the inner .wall portions of the ingot moldbelow and above the shoulder portion 16 may be formed with surfacesslightly inclined to the vertical and also to the surface of shoulderportion 16. The space-14 between casing 13 and upper part 17 of theingot mold is filled with sand, bricks or another. insulating material.It is naturally also possible to effect mold insulation by enclosing airin a suitable manner in the space 14.- Before or after the applicationof the casing ,it may be desirable to apply a sealing medium, such asasbestos, putty, wood wool, straw, glass wool or the like on or close tothe contact surface of the ingot mold and the casing 13 as at 15, 16.

In .FIG. 4 is shown an embodiment in which the ingot mold .12terminatesatits upper end adjacent the shoulder portionl. .Above the ingot mold isplaced an outer casingt19 of aninsulating material, such as insulatingbricks, surrounded by an outershell 20, and this outer casing 19laterally supports the outer surface of the hot top casing. Betweentheouter casing 19: andthe hot top casing 13 is arranged a space 14.

Other modifications of the hot top casing are possible, The outersurface of the hot top casing may extend'into the upper portion of theingotmold. In FIG. is shown a hot.top, corresponding with that of FIG.'3, at the upper portion of which is provided a cover 18 above. thespace 14, which space is filled with insulating ,.material, such asbricks.

The hot top casing 13 has been illustrated in FIGS. l,6 as taperingupwardly ,and inwardly toward the center of the ingot mold, but thecasing may also have substantially vertical walls as illustrated in FIG.7.

,A hot top casing formed in accordance with FIGS. 1-5 and' 7 with orWithout the last mentioned cover provides the great advantage that steelor the like from the bloom 'does not to any substantial degree penetratebetween the casing and the innerwall of the ingot mold, on account ofwhichthe risk of hot cracks in the outer layer of the ingot inconnection with the stilfening of the ingot is avoided. ,Further .thereis obtained a smooth travel bef. tween hot top and ingotmold and in theingot the forma tion of pads or any other protuberances is avoided,which flaws ordinarily would have been impossible to removeconsequently, the percentage of scrap in In. the embodimentsdescribedabove with reference to :FIGS. 1-5 and 7, thelower extremity ofthe casing 13 is tapered and the outer surfaceof the tapered portioninclined surfaces 22 joined by a common edge 23, which surfaces arecontiguous with the walls of a corresponding ledge in the inner wall ofthe mold.

The thickness of the casing (13, 21) above the lower end supportingsurface or surfaces (15, 22) is generally constant and preferablybetween 5 and 15 mm. For a 1.7-ton ingot the casing thickness should beapproximately 12 mm. 7

While in accordance with the patent statutes I have illustrated anddescribed the best forms and embodiments of my invention now known tome, it will be apparent to those skilled in the art that other changesmay be made in the apparatus described without deviating from theinvention as set forth in the following claims.

I claim:

1. A hot top casing for an ingot casting mold consisting of a moldedmixture of from 2 to 15% by weight of a fibrous organic material, 4 to10% by weight of a binder, up to 4% by weight of an inorganic fibrousmaterial and the remainder consisting essentially of a granular fireproof material which is not disintegrated by the heat to which it issubjected in use selected frornthe group consisting of quartz, sand,refractory silicates, burned dolomite and cinders, said granularfireproof material having a medium grain size within the range from 0.6to 0.05 mm. and said casing beingrelatively thin andhaving asmooth innersurface.

2. A hot top casing as defined in claim 1 wherein said binderis anorganic glue.

3. A hot top casing asdefined in claim 1 wherein said fireproof materialis quartz.

4. A hot top casing as defined in claim 1 wherein said organic fibrousmaterial includes cellulosic fibers less than 8% by weight, and saidbinder includes glue in the range of 48%.

5. A hot top casing as defined in claiml in which the percentage offibrous organic material is within the range from 2.5% to 13%.

6. A hot top casing for an ingot casting mold consist: ing of a molded'mixture of from 2 to 15% by weight of a cellulose fibrous organicmaterial,.4 to 10% by weight of aresin binder, up to 4% by weight of aninorganic fibrous material and the remainder consisting essentially of agranular fireproof material which is not disintegrated by the heat towhich it is subjected in use consisting of refractory silicatecontaining material, said granular firetively thin and having a smoothinner surface.

References Cited in the file of this patent UNITED STATES PATENTS1,696,986 Trembour .'Ian. 1, 1929 1,795,011 :Cross .Mar. 3,.19311,819,364 Firth et a1. Aug.. 18, 1931 2,148,583 .Rowe Feb. 28,19392,231,813 McDonald Feb. 11,1941 2,272,018 Nicholas .'Feb. 3, 19422,462,255 Charman et a1 Feb. 22, 1949 2,678,481 Peterson .May 18, 19542,952,055 Gottschalk Sept. 13, 1960

1. A HOT TOP CASING FOR AN INGOT CASTING MODE CONSISTING OF A MOLDEDMIXTURE OF FROM 2 TO 15% BY WEIGHT OF A BINDER, A FIBROUS ORGANICMATERIAL, 4 TO 10% BY WEIGHT OF A BINDER, UP TO 4% BY WEIGHT OF ANINORGANIC FIBROUS MATERIAL AND THE REMINDER CONSISTING ESSENTIALLY OF AGRANULAR FIREPROOF MATERIAL WHICH IS NOT DISINTEGRATED BY THE HEAT TOWHICH IT IS SUBJECTED IN USE SELECTED FROM THE GROUP CON SISTING OFQUARTZ, SAND, REFRACTOR SILICATES, BURNED DOLOMITE AND CINDERS, SAIDGRANULAR FIREPROOF MATERIAL HAVING A MEDIUM GRAIN SIZE WITHIN THE RANGEFROM 0.6 TO 0.05 MM. AND SAID CASING BEING RELATIVELY THIN AND HAVING ASMOOTH INNER SURFACE.